Objective: To determine the proportion of asthma patients with a poor perception of dyspnea, correlating the level of that perception with the severity of acute bronchoconstriction, bronchial hyperresponsiveness, use of maintenance medication, and asthma control. Methods: Uncontrolled clinical trial involving asthma patients treated at the Pulmonology Outpatient Clinic of the São Lucas Hospital, in Porto Alegre, Brazil. Methacholine challenge testing was performed using a five-breath dosimeter protocol. The perception of dyspnea after each breath was determined using the Borg scale. Data concerning asthma control, medication in use, and use of rescue short-acting bronchodilators were recorded. Results: Of the 65 patients included in the study, 53 completed the evaluation. Of those, 32 (60.5%) showed adequate perception of dyspnea after the methacholine challenge test, whereas 21 (39.5%) did not perceive any changes in the degree of dyspnea even after a 20% fall in FEV1. There were no significant differences between the two groups regarding baseline FEV1, percentage fall in FEV1, and the dose of methacholine causing a 20% fall in FEV1. The perception of dyspnea was not significantly associated with age (p = 0.247); gender (p = 0.329); use of maintenance medication (p = 0.152); asthma control (p = 0.562), bronchial hyperresponsiveness (p = 0.082); or severity of acute bronchoconstriction (p = 0.749). Conclusions: A significant proportion of asthma patients have a poor perception of dyspnea. The factors related to the inability of these patients to identify changes in pulmonary function have not yet been well defined. In order to reduce asthma-related morbidity and mortality, it is essential that this group of patients be identified and counseled.

Keywords: Asthma; Dyspnea; Airway obstruction.

Introduction: A considerable increase in asthma and atopy prevalence has been noticed worldwide through the last decades, however, in our country, epidemiological data are still insufficient. Objective: This study was carried out to determine the prevalence of asthma and atopy in a group of students, and compare these data with those found in two previous studies undertaken in Porto Alegre, Rio Grande do Sul. Methods: Asthma prevalence was identified through a questionnaire applied to 855 students from five schools of Porto Alegre. The students submitted to skin tests who presented, at least, one positive reaction were considered atopic. The signature of an informed consent from one of the parents was required for the skin test performance. Results: Prevalence was found to be 42.5% and 22% of cumulative and active asthma, respectively, with predominance in females. Atopy was identified in 50.1% of the sample. These results were significantly higher than the 6.7% (1980) and 16% (1989) of cumulative asthma, 10.9% (1989) of active asthma and 15.8% (1980) of atopy found in the two previous studies. Conclusion: A high prevalence of asthma and atopy was identified in our students. Future studies should be performed to elucidate the phenomenon herein demonstrated.

Keywords: Asthma. Epidemiology. Atopy.